Electric stimulation of cells and tissues is the basis of diverse medical treatments. However, stimulation of deep structures is usually invasive and relies on electrodes that are inserted or permanently implanted into the body. Transcranial magnetic stimulation (TMS) is an example of a non-invasive technology, but its penetration depth and precision are limited. Thus far, deep-penetrating but non-invasive electrostimulation has not been possible. However, recent developments in picosecond pulse technology offer an opportunity to overcome physical limitations and to deliver electric stimuli deep into the human body without using electrodes. We propose to employ intense picosecond-duration electric pulses (psEP) as a substitute for conventional electric stimulation with longer (micro- and millisecond) pulses. Instead of electrodes, psEP can be delivered by ultrawideband antennas in the form of electromagnetic waves, and focused at a depth in the human body without insertion of electrodes. Computer simulations predict significantly deeper penetration and better focusing of 200-ps pulses in comparison with TMS. Also, we have assembled and tested a prototype of an in vitro psEP exposure system and, for the first time, were able to demonstrate that 200-ps EP can indeed evoke action potentials in cultured neurons. This interdisciplinary project combines an engineering effort to develop and characterize psEP exposure systems with biological analyses of the efficiency and safety of electrostimulation by psEP. Specifically, this project consists of five Aims intended to 1) develop a microscopy- and patch clamp- compatible system for psEP studies in vitro, 2) perform high-resolution computer simulations of psEP delivery in a realistic human head model, 3) quantify electrostimulation parameters in vitro for single pulses and trains of 200-ps pulses, 4) analyze Ca2+ dynamics in psEP-treated excitable and non-excitable cells, and 5) determine the safety margin between stimulatory effects and cell damage. This study will provide guidance for engineering of a high voltage picosecond pulser and antenna for deep-brain stimulation. It will also lay the ground for first in vivo trials of no-invasive psEP electrostimulation.